What Causes Specific Language Impairment in Children?
Dorothy V.M. Bishop
Current Directions in Psychological Science 2006 15: 217
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CU R RE N T D I R E CT I O NS IN P SYC H OL OG I C AL SC I EN C E
What Causes Specific Language
Impairment in Children?
Dorothy V.M. Bishop
University of Oxford, Oxford, England
OnlineOpen: This article is available free online at www.blackwell-synergy.com
language impairment (SLI) is diagnosed when a child’s language development is deﬁcient for no obvious reason. For many years, there was a tendency to assume that SLI was caused by factors such as poor parenting, subtle brain damage around the time of birth, or transient hearing loss. Subsequently it became clear that these factors were far less important than genes in determining risk for SLI. A quest to ﬁnd ‘‘the gene for SLI’’ was undertaken, but it soon became apparent that no single cause could account for all cases. Furthermore, although fascinating cases of SLI caused by a single mutation have been discovered, in most children the disorder has a more complex basis, with several genetic and environmental risk factors interacting. The clearest evidence for genetic effects has come from studies that diagnosed SLI using theoretically motivated measures of underlying cognitive deficits rather than conventional clinical criteria.
KEYWORDS—genetics; specific language impairment; twins;
Talking comes so naturally to most children that one seldom pauses to consider the enormous complexity of the achievement.
Understanding just how the human brain manages to learn language—typically in the space of around 4 short years—is still a long way off. Perhaps as remarkable as the speed with which young humans learn language is the robustness of this process in the face of adverse conditions (Bishop & Mogford, 1993). Most children will learn to talk adequately even if they are exposed to impoverished language input from adults or are visually impaired and thus unable to see what is being talked about. Children who are unable to speak because of physical disability, and those who cannot hear what others say to them, will nevertheless learn to
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Volume 15—Number 5
communicate by other means, provided they are exposed to alternative systems of communication such as sign language.
There are, however, exceptions to this general rule of speedy and robust language acquisition: Children with specific language impairment (SLI) have major problems in learning to talk, despite showing normal development in all other areas (see Table 1). Thus, a typical 7- or 8-year-old child with SLI may talk like a 3-year-old, using simpliﬁed speech sounds, with words strung together in short, ungrammatical strings—e.g., ‘‘me go there,’’ rather than ‘‘I went there.’’ SLI is a heterogeneous category, varying in both severity and proﬁle of